Post on 20-Jan-2016
transcript
Iodine Chemistry And It’s Iodine Chemistry And It’s Role In Ozone DepletionRole In Ozone Depletion
PRESENTED BY:PRESENTED BY:Farhana YasminFarhana Yasmin
IntroductionIntroductionOzone depletion in the troposphere has always been the main concern to the environment.
There are many factors, most of them coupled, that causes the depletion of the ozone, such as reactions and transport.
The reaction mechanism includes troposphericchemistry of ozone, hydrocarbon, nitrogen as well as sulfur and the halogens Cl, Br and I.
ObjectiveObjectiveModel of ozone depletion using FACIMILE that will allow us to investigate the effect of the iodine on ozone depletion.
Since iodine is a much more effective agent compared to bromine and chlorine, it is suspected that even in small amount iodine may have a profound impact on ozone depletion.
The modeling of ozone depletion will allow us to see the effect on the rate of ozone depletion with iodine concentration
OH/NOx CycleOH/NOx Cycle
OH HO2
NO2NO
O3
hv
hvH2O
CO
H2O2HO2DEPOSITION
HNO3
OH
HNO4
hv
Iodine CycleIodine Cycle
I
CH3I CH2I2 C3H7I CH2ClI
IO
hv hv hv hv
O3
+NO
+IO
I2O2
+IO
hv
HOI
HO2
hv
INO3+NO2
HI
I2
INO2+NO2
OH
hv
I-
HOIaqAerosol
OCEAN
PhotochemistryPhotochemistry
Photolysis Reactions J (1/s)O3 + hv-----> O('D)+O2 2.20E-05NO2+hv--->O3+NO 1.13E-02HNO4+hv---->NO2+HO2 5.00E-06INO2+hv-->I+NO2 2.90E-03IO+hv---> I+O3 2.20E-01INO3+hv--->IO+NO2 2.90E-03HOI+hv---->I+OH 5.90E-03I2O2+hv----->2I+O2 1.30E-02I2+hv----> 2I 1.20E-01
Bimolecular ReactionBimolecular Reaction
RT
EAk exp*
k = rate constant A = Pre-exponential constantE = activation EnergyR = Gas constantT = Temperature in K
Arrhenius Equation
Binary Reaction k (cm3molecule-1s-1)O('D)+M=O+M 3.60E-11
O('D)+H2O--->OH+OH 2.20E-10OH+CO---.>HO2+CO2 9.60E-13HO2+NO---->OH+NO2 1.29E-12OH+H2O2--->HO2+H20 1.53E-12HO2+HO2--->H2O2+O2 2.09E-14H2O2----> depH2O2 (1/s) 2.31E-06HNO3---.>depHNO3 (1/s) 2.31E-06
I+O3----IO+O2 5.69E-13I+HO2---->HI+O2 1.92E-13IO+NO---->I+NO2 2.73E-11
IO+HO2---->HOI+O2 8.40E-11IO+IO-----> I2O2 5.20E-11
IO+IO----> I+I+O2 2.80E-11HI+OH---->I+H2O 3.00E-11
HOI+OH---->IO+H2O 2.00E-13
Termolecular ReactionsTermolecular Reactions
30030000
Tkk
300
300 Tkk
The low pressure-limiting rate constant The high pressure-limiting rate constant
ABABBA kkk 211 *][/ M
Effect Second Order Rate Constant
k
Mk
f
k
MkMk
TMk
][*log1
0
0
010
6.0*][*
1
][*)],([
OH + NO2 + M -------> HNO3 + MHO2 +NO2 + M ----- HNO4 + M
I + NO2 + M -------> INO3 + M
IO + NO2 + M ----- INO3 + M
Heterogeneous ReactionsHeterogeneous Reactions
HI(g) ↔ Iֿ aqHOI(g) ↔ HOIaq
Avk f 4
1
M
RTv
8
3
3
__
__**cmvolumeair
cmvolumeaeresol
atm
airfb V
V
P
N
H
kk
Forward Reaction:
Backward Reaction
Effect of I and IO on Ozone DepletionEffect of I and IO on Ozone Depletion
Effect of I and IO on ozone depletion
0.00E+00
2.00E+10
4.00E+10
6.00E+10
8.00E+10
1.00E+11
1.20E+11
1.40E+11
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000
Time (sec)
O3
(m
ole
cu
les
/cm
^3
)
I= 7pptv , IO= 2 pptv I=9pptv, IO = 3pptv I=20pptv, IO=4pptv I=27pptv, IO=6pptv
Effect of O3 concentration on IodineEffect of O3 concentration on IodineEffect on O3 Concentration on I
0.00E+00
1.00E+08
2.00E+08
3.00E+08
4.00E+08
5.00E+08
6.00E+08
7.00E+08
0 50000 100000 150000 200000 250000
Time (sec)
I (m
ole
cu
les
/cm
^3
)
O3 1ppbv O3 5ppbv O3 10ppbv
Effect of NOx on Ozone DepletionEffect of NOx on Ozone Depletion
Effect of NOx on ozone depletion
0.00E+00
2.00E+10
4.00E+10
6.00E+10
8.00E+10
1.00E+11
1.20E+11
1.40E+11
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000
Time (sec)
O3
(mo
lecu
les/
cm^
3)
NO= 0, NO2=0 NO= 2.9pptv, NO2=2.4pptv NO=6.1pptv, NO2=4.8pptv
Effect of NOx on Ozone DepletionEffect of NOx on Ozone DepletionEffect of NOx on ozone depletion
0.00E+00
1.00E+08
2.00E+08
3.00E+08
4.00E+08
5.00E+08
6.00E+08
7.00E+08
8.00E+08
9.00E+08
1.00E+09
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000
Time (sec)
O3
(mo
lecu
les/
cm^
3)
NO= 0, NO2=0 NO= 2.9pptv, NO2=2.4pptv NO=6.1pptv, NO2=4.8pptv
ConclusionConclusion• The magnitude of catalytic ozone destruction depends on the amount of reactive iodine present.
• As the iodine concentration increases the ozone depleted faster
• O3 depletion rate increases as NOx concentration is decreased
• I reaches steady state faster as O3 concentration decreases
RecommendationsRecommendations
• This study is highly theoretical and our conclusions, therefore, strongly need testing with observational data.
• Further identification of the marine biological processes leading to the production of organic iodine gases and their releases to the atmosphere.
• Problems using FACSIMILE:• Easy to make mistake• Does not allow to add reactions• Order of reaction matters